Originally reported: 23 August 2026
This is the source report date, not necessarily the date of the event.
A 24‑day voyage aboard CSIRO’s RV Investigator collected seabed cores that show the Great Barrier Reef was once dry land, exposing submerged rivers, lakes and an ancient coral platform.
On the southern flank of the Great Barrier Reef, CSIRO’s research vessel RV Investigator set sail from the Capricorn Bunker Group for a 24‑day expedition that blended oceanography with Indigenous knowledge. The ship, operating off the Yeppoon and Gladstone coasts, carried a team of marine scientists, University of Queensland researchers and Darumbal and Woppaburra rangers. Together they gathered seabed sediment cores from water depths ranging between 50 and 200 metres, targeting sites where ancient landforms were suspected.
The core samples, later washed aboard the vessel by the rangers, revealed layers of microfossils, pollen and other micro‑remains that pointed to a dramatically different seascape. Analyses showed that around 65,000 years ago sea level stood about 80 metres lower, exposing a network of rivers, lakes, estuaries and even a beach‑type shoreline where the modern reef now sits. In one location near Swain Reef, scientists identified a drowned coral reef that had once thrived in shallow, sun‑lit waters.
Helen Bostock of CSIRO highlighted how the sediment record offers a timeline that predates the modern oceanographic data, which are expected to be released within the next year. While oceanographic instruments provide rapid snapshots of temperature and currents, the sediment work will take longer to interpret but promises a richer picture of past climate and sea‑level fluctuations.
Indigenous participation was integral to the project’s design. Darumbal and Woppaburra rangers, including Tshinta Barney and Nataliah Backo, helped with sample handling and contributed oral histories that align with the physical evidence of ancient waterways. Their involvement underscores a growing partnership model where traditional owners guide scientific inquiry into sea‑country changes.
The expedition also mapped a previously unknown submerged river system that once cut across what is now the central Queensland reef zone. By tracing the sediment signatures, researchers can reconstruct the ancient drainage patterns that fed freshwater into the marine environment, offering clues about nutrient flows and ecosystem dynamics that shaped early reef development.
Looking ahead, the team plans to transform the core data into detailed maps of the ancient landscape. These reconstructions will serve both cultural heritage documentation for Indigenous communities and practical inputs for contemporary reef‑health assessments. By comparing past and present conditions, scientists hope to refine models that predict how the reef will respond to ongoing sea‑level rise and climate stressors.
The findings, announced shortly after the expedition’s return, add a new dimension to our understanding of the Great Barrier Reef’s geological legacy. They also illustrate how collaborative science, anchored in Indigenous stewardship, can uncover hidden chapters of Australia’s marine past while informing future conservation strategies.
Why this matters
Revealing the reef’s ancient topography helps scientists calibrate sea‑level models, improves predictions of coral resilience, and honours Indigenous connections to a landscape that existed long before modern shorelines.
What happens next
Researchers will finish sediment analysis, publish the reconstructed maps and integrate the data into reef‑health monitoring programmes slated for release next year.
Marine science glossary
- Sediment core
- A cylindrical sample taken from the seabed that preserves layers of deposited material, useful for reconstructing past environmental conditions.
- Microfossils
- Tiny fossilised remains of organisms such as plankton that provide clues about historic water chemistry and climate.